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-rw-r--r--guix/build/syscalls.scm27
1 files changed, 27 insertions, 0 deletions
diff --git a/guix/build/syscalls.scm b/guix/build/syscalls.scm
index d75c11ada7..66d63a2931 100644
--- a/guix/build/syscalls.scm
+++ b/guix/build/syscalls.scm
@@ -73,6 +73,7 @@
file-system-mount-flags
statfs
free-disk-space
+ device-in-use?
processes
mkdtemp!
@@ -684,6 +685,32 @@ mounted at FILE."
(define AT_NO_AUTOMOUNT #x800)
(define AT_EMPTY_PATH #x1000)
+(define-syntax BLKRRPART ;<sys/mount.h>
+ (identifier-syntax #x125F))
+
+(define* (device-in-use? device)
+ "Return #t if the block DEVICE is in use, #f otherwise. This is inspired
+from fdisk_device_is_used function of util-linux. This is particulary useful
+for devices that do not appear in /proc/self/mounts like overlayfs lowerdir
+backend device."
+ (let*-values (((fd) (open-fdes device O_RDONLY))
+ ((ret err) (%ioctl fd BLKRRPART %null-pointer)))
+ (close-fdes fd)
+ (cond
+ ((= ret 0)
+ #f)
+ ((= err EBUSY)
+ #t)
+ ((= err EINVAL)
+ ;; We get EINVAL for devices that have the GENHD_FL_NO_PART_SCAN flag
+ ;; set in the kernel, in particular loopback devices, though we do seem
+ ;; to get it for SCSI storage (/dev/sr0) on QEMU.
+ #f)
+ (else
+ (throw 'system-error "ioctl" "~A"
+ (list (strerror err))
+ (list err))))))
+
;;;
;;; Containers.